There are well-known measurement acquisition and transmission systems utilizing sensors associated with bottomhole electronics, such as those transmitting their information by pressure wave in the mud, or by electromagnetic wave. But the number of parameters transmitted is small and the transmission rate is relatively low.
In, for example, FR-2,645,205 and U.S. Pat. No. 4,715,451 a well-known measuring systems are located at the top of the drill string, near the surface. But the object of these techniques is not to use bottomhole sensors.
Furthermore, none of these documents suggests the use or the possibility of synchronizing two measuring sources arranged substantially at each end of the drill string.
On the contrary, the object of a preferred embodiment according to the present invention is to provide a system for the real time transmission of a large number of data, coming notably from sensors close to the drill bit and from surface sensors, and at the same time the possibility of recording them synchronously by a surface processing installation. In fact, it has been found, in accordance with the present invention, that comprehension and, consequently, modeling of the drilling process can only be achieved if a certain number of parameters are measured at several points of the drill string. Since drilling is a highly dynamic process, a number of these parameters have to be measured at a high rate and with a sufficient synchronization precision.